A number of systems to join pipes is already known. A first family of these joining systems requires that the pipe has been previously threaded in order to allow the fastening of the joining means. A second family of these joining systems is preferably applied to pipes of soft materials, such as polyethylene (PE), polybutylene (PB), etc., and makes use of the strain capacity of the pipe for it to become compressed in the joining means, but most of these joints do not get a suitable fastening and sealing before high pressures in the network, or before axial displacements of the sections of the pipes. In order to solve this problem, fittings for pipes have been proposed having the means to produce a thread in them in the very operation of installing the fitting. This type of solutions, however, forces the material to be harder than the material of the pipe, and does not ensure a good stability of the joint in case of bendings in the joining zone.
The present invention, on the contrary, allows a pipe joining which is resistant in case of axial displacements or bendings of the pipe, keeping its watertightness characteristics, this avoiding the leakages of flow in the network.
In addition, it allows that one of its components, that is, the threaded joining end, be harder than the pipe, and, as explained below, this ensures more stable and safer joinings of pipes.